svn commit: r259609 - head/sys/kern

[Stefan Esser]

Author: se
Date: Thu Dec 19 09:01:46 2013
New Revision: 259609
URL: http://svnweb.freebsd.org/changeset/base/259609

Log:
  Fix overflow for timeout values of more than 68 years, which is the maximum
  covered by sbintime (LONG_MAX seconds).
  
  Some programs use timeout values in excess of 1000 years. The conversion
  to sbintime caused wrap-around on overflow, which resulted in short or
  negative timeout values. This caused long delays on sockets opened by
  affected programs (e.g. OpenSSH).
  
  Kernels compiled without -fno-strict-overflow were not affected, apparently
  because the compiler tested the sign of the timeout value before performing
  the multiplication that lead to overflow.
  
  When the -fno-strict-overflow option was added to CFLAGS, this optimization
  was disabled and the test was performed on the result of the multiplication.
  Negative products were caught and resulted in EINVAL being returned, but
  wrap-around to positive values just shortened the timeout value to the
  residue of the result that could be represented by sbintime.
  
  The fix is to cap the timeout values at the maximum that can be represented
  by sbintime, which is 2^31 - 1 seconds or more than 68 years.
  
  After this change, the kernel can be compiled with -fno-strict-overflow
  with no ill effects.
  
  MFC after:	3 days

Modified:
  head/sys/kern/kern_event.c

Modified: head/sys/kern/kern_event.c
==============================================================================
--- head/sys/kern/kern_event.c	Thu Dec 19 07:33:07 2013	(r259608)
+++ head/sys/kern/kern_event.c	Thu Dec 19 09:01:46 2013	(r259609)
@@ -526,7 +526,8 @@ knote_fork(struct knlist *list, int pid)
 static __inline sbintime_t 
 timer2sbintime(intptr_t data)
 {
-
+	if (data > LLONG_MAX / SBT_1MS)
+		return LLONG_MAX;
 	return (SBT_1MS * data);
 }